Pipe joint reducing required tightening force, including a tightening nut with two threaded sections whose pitches differ

ABSTRACT

A pipe joint for joining a tubular component ( 1 ) to a receiving piece ( 2 ), the pipe joint comprising a fitting body ( 3 ) having a recess ( 8 ), a tightening nut ( 6   a ) having a first thread ( 7   a ), the fitting body having a corresponding thread ( 4 ), and a cutting ring ( 9 ) being arranged to be pressed between a wedge-like wall portion ( 10 ) of the recess, and the tubular component when the tightening nut is tightened. In order that the pipe joint could be tightened to form a leak-proof and strong joint using low torque, which enables the use of small tools applicable in confined spaces, the pipe joint comprises a supplementary nut ( 6   b ) having a thread ( 7   c ) whose handedness corresponds to that of the first thread ( 7   a ) but is smaller, the tightening nut comprising a second thread ( 7   b ) corresponding to that of the supplementary nut.

BACKGROUND OF THE INVENTION

The invention relates to a pipe joint for joining a tubular component toa receiving piece, the pipe joint comprising a fitting body having arecess for receiving the tubular component, a tightening nut having afirst thread and a second thread, the fitting body having a first threadcorresponding to the first thread of the tightening nut, and a cuttingring between the tightening nut and the fitting body, the cutting ringbeing arranged to be pressed between a wedge-like wall portion of therecess, and the tubular component when the tightening nut is tightened.The tightness of the joint is based on sealing achieved by the metallic“cutting ring”. In this context, the term receiving piece refers to anypoint of attachment used in various applications of the pipe joint. Forexample, the receiving piece can be a wall of a container or arecipient, a pump, a thread of a tubular component, etc.

From DIN standard No. 2353 is known a joint whose tightness is not basedon the use of a seal made of rubber material but on the sealing providedby a metallic cutting ring. When the tightening nut is turned towardsthe fitting body, the cutting ring presses in a wedge-shaped spacetowards the first tubular component cutting into an outer surfacethereof and tightening against it, and at the same time it tightenstowards inner surfaces of the tightening nut and the fitting body. Thetighter the nut is turned, the closer the cutting ring cuts in the pipeand the joint becomes stronger. The DIN standard defines fittings forpipe diameters of 4 to 42 mm. The pitch of a thread at a first end ofthe fitting body, i.e. of a first thread, is 1 to 2 mm depending on thepipe size, so that the wider the pipe, the larger the pitch.

To provide the above-described sealing, the tightening nut must beturned with sufficient force. The tightening nut of a large joint mustbe turned with greater torque than the tightening nut of a small joint.

A problem with the above-described known joints can be that the torquerequired by the tightening nut is great particularly when large-diameterpipes are concerned. This problem becomes more apparent if the joint islocated in a confined space without any room for big tools. Instead, onehas to use a small tool that must be wrenched with great force in aconfined space so as to achieve a sufficient torque and a firm joint. Byusing a smaller pitch in a tightening nut/fitting body combination therequired torque would be lower, but firstly, fittings of this kind arenot available, because the fitting bodies are standardized havingrelatively large pitches, and secondly, a smaller pitch is technicallymore difficult to manufacture than a larger pitch. Moreover, a veryconsiderable fact is that a fine and long thread would be slow to mount.

BRIEF DESCRIPTION OF THE INVENTION

The object of the present invention is to provide a joint which canreadily be tightened leak-proof and strong, even with small tools and inconfined spaced, and nevertheless, which allows the use of astandardized fitting body.

For this purpose the present invention provides, according to one aspectthereof a pipe joint for joining a tubular component to a receivingpiece, the pipe joint comprising a fitting body having a recess forreceiving the tubular component, a tightening nut having a first threadand a second thread, the fitting body having a first threadcorresponding to the first thread of the tightening nut, and a cuttingring between the tightening nut and the fitting body, the cutting ringbeing arranged to be pressed between a wedge-like wall portion of therecess, and the tubular component when the tightening nut is tightened,and a supplementary nut having a thread whose handedness and pitchcorresponds to the second thread of the tightening nut and whosehandedness corresponds to that of the first thread of the tighteningnut, and wherein the pitch of the thread of the supplementary nut issmaller than the pitch of the first thread of the tightening nut, andthe tightening nut is designed not to contact the cutting ring whentightening it.

For said purpose the present invention provides, as an alternative, apipe joint for joining a tubular component to a receiving piece, thepipe joint comprising a fitting body having a recess for receiving thetubular component, a tightening nut having a first thread and a secondthread, the fitting body having a first thread corresponding to thefirst thread of the tightening nut, and a cutting ring between thetightening nut and the fitting body, the cutting ring being arranged tobe pressed between a wedge-like wall portion of the recess, and thetubular component when the tightening nut is tightened, and asupplementary nut having a thread whose handedness and pitch correspondsto the second thread of the tightening nut and whose handednesscorresponds to that of the first thread of the tightening nut, andwherein the pitch of the thread of the supplementary nut is 20 to 80% ofthe pitch of the first thread of the tightening nut.

The cutting ring is arranged to press against the supplementary nut andthe fitting body as the tightening nut is tightened. This ensures thatthe force acts on the cutting ring as intended.

It can be said that the supplementary nut according to the inventionchanges the gear ratio of the tightening nut thread: when the tighteningnut is turned n turns, the cutting ring does not press/shift for adistance S1=n×p, where p is the pitch of the fitting body, but thecutting ring presses/shift for a distance S2=n×p−n×p2, where p2 is thepitch of the supplementary nut, with the proviso that the supplementarynut is held in place to prevent it from turning while the tightening nutis turned. If the pitch p2 of the supplementary nut is close to thepitch p of the fitting body, an easily manufactured joint is obtained(because the thread pitch is relatively high), in which the cutting ringpresses/is displaced only for a short distance, even though thetightening nut is turned several rounds n. A great force is transferredto the cutting ring by a small force acting on the tightening nut.

When the first thread of the tightening nut is an internal thread, thefirst thread of the fitting body is an external thread and the fittingbody can be a DIN standard body. In addition, if the second thread (I)of the tightening nut is provided on the inner circumference of thetightening nut, the threads of the tightening nut are well protectedagainst external impacts, if any, in the finished joint. Advantageously,the diameter (I) of the thread of the supplementary nut is smaller thanthe diameter of the first thread (f) of the tightening nut, wherebythere is space for the supplementary nut to enter deep inside thetightening nut, in a space inside the first thread thereof, andconsequently the joint becomes compact, tight for its size, and theallowance for joint adjustment becomes large.

The thread pitch of the supplementary nut is preferably 20 to 80%, andin many applications more preferably 20 to 60% of the pitch of the firstthread (f) of the tightening nut.

The outer circumference of the supplementary nut is preferably smallerthan the outer circumference of the tightening nut, which makes it veryeasy to apply the tools to nut surfaces, and it is extremely easy totighten the joint and correspondingly to open it, if necessary.

The fitting body preferably comprises a nut-shaped outer circumference,which is smaller in size than the outer circumference of the tighteningnut. Thus, the fitting body is preferably of standard size.

The inner diameter of the supplementary nut preferably corresponds tothe diameter of the recess in the fitting body, and the inner surface ofthe supplementary nut fits on the outer surface of the tubular componentsupporting radially said tubular component.

At one end the supplementary nut preferably comprises a conical portion,whose inner diameter increases towards said end. Hence, the conicalportion directs the force exerted on the cutting ring such that thecutting ring is effectively pressed onto the surface of the tubularcomponent as the supplementary nut is turned.

Major advantages of the pipe joint according to the invention are thatit can be tightened leak-proof and strong readily and quickly using lowtorque, which enables the use of small tools suitable for small spaces,if necessary. The above advantages are most apparent when large pipeshaving diameters of e.g. 30 to 80 mm are used. The pipe joint is easy tomake and it allows the use of a standardized fitting body, which isnaturally advantageous.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described in greater detail, bymeans of one preferred embodiment, with reference to the attacheddrawing, wherein

FIG. 1 shows a prior art pipe joint, and

FIGS. 2 to 4 show a pipe joint according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a known pipe joint for joining a pipe 1′ or a tubularcomponent to a receiving piece 2′, for instance to a wall of a container2 a′, a pump (not shown) or a tubular component (not shown). The pipejoint comprises a fitting body 3′, at a first end of which there is afirst external thread 4′ and at the opposite end a second externalthread 5′. The first thread 4′ receives a corresponding internal thread7′ of a tightening nut 6′. Reference numeral 8′ designates a recess inthe fitting body for receiving the end 12′ of the pipe 1′. Referencenumeral 9′ designates a cutting ring, which is positioned in part in aconical, i.e. wedge-like, wall portion 10′ and in part in a conicalportion 1′ of the tightening nut 6′. As can be seen from FIG. 1, thewall portion 10′ adjoins to the recess 8′ and thus actually defines inpart the recess 8′. As the tightening nut 6′ is turned, the cutting ring9′ presses against the surface of the pipe 1′ and provides sealing. Themore the tightening nut 6′ is turned, the closer the cutting ring cutsinto the surface of the pipe and the stronger the joint will be. Thepipe 1′ is e.g. 42 mm in diameter and the pitch of the fitting bodythread 4′ is 2 mm. So, when the tightening nut 6′ is turned one round,the tightening nut shifts 2 mm to the right. The external thread 5′ isfor attachment to the receiving piece 2′.

FIG. 2 shows a pipe joint according to the invention. FIG. 3 shows thejoint of FIG. 2 when tightened up into a firm joint.

The fitting body 3 of the pipe joint corresponds to the fitting body 3′of FIG. 1 and is in accordance with DIN standard No. 2353. The pipejoint of the figure differs from that of FIG. 1 in such a way that,instead of one single tightening nut, the joint comprises two nuts: atightening nut 6 a and a so-called supplementary nut 6 b. The tighteningnut 6 a comprises a first thread 7 a, whose pitch corresponds to thepitch of the thread 4 in the fitting body. The tightening nut 6 acomprises a second internal thread 7 b, the supplementary nut 6 b havinga corresponding external thread 7 c. The turning direction of theinternal thread 7 b corresponds to that of the first thread 7 a but thepitch is lower. The pitch of the first thread 7 a is 2 mm and the pitchof the internal thread 7 b is 1 mm. Naturally, the above values are justexamples. More generally, it can be said that the pitch of the thread 7b is 20 to 80% of the pitch of the thread 7 a, whereby the range of 20to 60 would cover most of the practical applications. If the pitch ofthe thread 7 b were extremely low, the manufacturing thereof wouldbecome difficult.

The pipe 1 of FIG. 2 can be sealed to the fitting body 3 such that thetightening nut 6 a, the supplementary nut 6 b and the cutting ring 9 aremounted round the pipe end, and then the pipe end is inserted in therecess 8 of the fitting body. Thereafter, the tightening nut 6 a isturned so that the cutting ring 9 fits against the wall portion 10 ofthe fitting body 3 and against a conical portion at the end of thesupplementary nut. After that, tightening of the tightening nut 6 a iscontinued, and simultaneously, the supplementary nut 6 b is held inplace such that it will not turn with respect to the fitting body.Hence, as the tightening nut 6 a is turned two rounds, for instance, itmoves 2×2=4 mm to the right. However, the supplementary nut 6 b movessimultaneously 2×1 mm=2 mm to the left with respect to the tighteningnut 6 a, whereby the supplementary nut 6 b presses the cutting ring4−2=2 mm to the right axially. Because of this, the force for turningthe tightening nut 6 a remains low as compared with the solution of FIG.1, even though the last mentioned needs to be turned only one round formoving the cutting ring 2 mm to the right.

FIG. 3 shows a leak-proof, strong joint, in which the cutting ring 9 iscut in the surface of the pipe 1.

As the inner diameter of the supplementary nut 6 b corresponds to theouter diameter of the pipe 1, the supplementary nut supports the piperadially.

The diameter of the first thread 7 a of the tightening nut 6 a exceedsthat of the second thread 7 b, whereby the end of the supplementary nut6 b can be inserted inside the thread 7 a. A compact pipe joint with alarge allowance for adjustment/tightening is thus achieved. The outercircumference of the supplementary nut 6 b is smaller than the outercircumference of the tightening nut 6 a, and consequently tools can beeasily applied to the nuts.

FIG. 4 shows an axonometric view of the joint according to theinvention.

In the above, the invention is only described by means of one preferredembodiment, and therefore it should be noted that the details of theinvention can be implemented in a variety of ways within the scope ofthe accompanying drawings. Thus, the tightening nut, for instance, mayat least in principle comprise an external thread, instead of theinternal thread, and consequently the supplementary nut shouldcorrespondingly comprise an internal thread. However, the lattersolution would make the fitting larger and external threads would beexposed to external impacts. Application of tools would also be moredifficult.

1. A pipe joint for joining a tubular component to a receiving piece,the pipe joint comprising a fitting body having a recess for receivingthe tubular component, a tightening nut having a first thread and asecond thread, the fitting body having a first thread corresponding tothe first thread of the tightening nut, and a cutting ring between thetightening nut and the fitting body, the cutting ring being arranged tobe pressed between a wedge-like wall portion of the recess, and thetubular component when the tightening nut is tightened, and asupplementary nut having a thread whose handedness and pitch correspondsto the second thread of the tightening nut and whose handednesscorresponds to that of the first thread of the tightening nut, andwherein the pitch of the thread of the supplementary nut is smaller thanthe pitch of the first thread of the tightening nut, and the tighteningnut is designed not to contact the cutting ring when tightening it.
 2. Apipe joint for joining a tubular component to a receiving piece, thepipe joint comprising a fitting body having a recess for receiving thetubular component, a tightening nut having a first thread and a secondthread, the fitting body having a first thread corresponding to thefirst thread of the tightening nut, and a cutting ring between thetightening nut and the fitting body, the cutting ring being arranged tobe pressed between a wedge-like wall portion of the recess, and thetubular component when the tightening nut is tightened, and asupplementary nut having a thread whose handedness and pitch correspondsto the second thread of the tightening nut and whose handednesscorresponds to that of the first thread of the tightening nut, andwherein the pitch of the thread of the supplementary nut is 20 to 80% ofthe pitch of the first thread of the tightening nut.
 3. A pipe joint asclaimed in claim 1, wherein the pitch of the thread of the supplementarynut is 20 to 80% of the pitch of the first thread of the tightening nut.4. A pipe joint as claimed in claim 1, wherein the cutting ring isarranged to press against the supplementary nut and the fitting body asthe tightening nut is tightened.
 5. A pipe joint as claimed in claim 1,wherein the second thread of the tightening nut is provided on an innercircumference of the tightening nut, whereby the thread of thesupplementary nut is an external thread.
 6. A pipe joint as claimed inclaim 1, wherein first thread of the tightening nut is an internalthread, whereby the first thread of the fitting body is an externalthread.
 7. A pipe joint as claimed in claim 6, wherein the diameter ofthe thread of the supplementary nut is smaller than the diameter of thefirst thread of the tightening nut.
 8. A pipe joint as claimed in claim1, wherein the outer circumference of the supplementary nut is smallerin size than the outer circumference of the tightening nut.
 9. A pipejoint as claimed in claim 1, wherein the fitting body comprises anut-like outer circumference that is smaller in size than the outercircumference of the tightening nut.
 10. A pipe joint as claimed inclaim 1, wherein the inner circumference of the supplementary nut isequal to the diameter of the recess in the fitting body.
 11. A pipejoint as claimed in claim 10, wherein the supplementary nut comprises atone end a conical portion whose inner diameter increases towards saidend.
 12. A pipe joint as claimed in claim 1, wherein the fitting bodycomprises at an end opposing the recess a thread to be connected to thereceiving piece.
 13. A pipe joint as claimed in claim 2, wherein thecutting ring is arranged to press against the supplementary nut and thefitting body as the tightening nut is tightened.
 14. A pipe joint asclaimed in claim 2, wherein the second thread of the tightening nut isprovided on an inner circumference of the tightening nut, whereby thethread of the supplementary nut is an external thread.
 15. A pipe jointas claimed in claim 2, wherein first thread of the tightening nut is aninternal thread, whereby the first thread of the fitting body is anexternal thread.
 16. A pipe joint as claimed in claim 2, wherein theouter circumference of the supplementary nut is smaller in size than theouter circumference of the tightening nut.
 17. A pipe joint as claimedin claim 2, wherein the fitting body comprises a nit-like outercircumference that is smaller in size than the outer circumference ofthe tightening nut.
 18. A pipe joint as claimed in claim 2, wherein theinner circumference of the supplementary nut is equal to diameter of therecess in the fitting body.
 19. A pipe joint as claimed in claim 2,wherein the fitting body comprises at an end opposing the recess athread to be connected to the receiving piece.